The present invention relates generally to a crushed foam glass filter aid and methods for its use.
In a great many industrial processes a variety of filtering methods are utilized to separate one substance from another. In many of these processes a filtering aid is placed in a process stream to remove a waste product. Typically the filtering aid, such as diatomaceous earth, is placed adjacent to a permeable barrier, such as a screen. A process stream consisting of a fluid having impurities suspended therein is then directed through the filtering aid and the permeable barrier, whereupon the impurities become trapped on the filtering aid. As will be recognized by those having skill in the art, impurities may be trapped xe2x80x9conxe2x80x9d or xe2x80x9cwithinxe2x80x9d the filter aid, and as used herein xe2x80x9conxe2x80x9d should be understood to include any circumstance whereby impurities are so trapped by the filter aid. The impurities trapped within the filtering aid, together with the filtering aid itself, typically are then removed from the process together as waste.
These types of processes impose costs and inefficiencies on the over all process in at least two ways. First, the filtering aid is typically disposed of with the waste, resulting in an overall increase in waste volume and thus waste disposal costs. Second, a new filtering aid is then required for further filtering, imposing a recurring cost on the process each time filtering aid becomes loaded to capacity with waste.
Thus, there exists a need for improved filtering aids and methods of utilizing such filtering aids that minimize waste generation and disposal costs.
Accordingly, the present invention is a filter aid formed of a crushed foam glass. Any of the known methods for forming foam glass are suitable for the practice of the present invention, including but not limited to those described in U.S. Pat. No. 3,261,894 xe2x80x9cMethod of Manufacturing Foamed Silicate Structuresxe2x80x9d to Alois Seidl, U.S. Pat. No. 3,663,249 xe2x80x9cMethod for Insolubilizing Sodium Silicate Foamxe2x80x9d to Ramesh P. Rao, U.S. Pat. No. 3,743,601 xe2x80x9cProcess for Making Silicate Foams from Alkali Metal Silicatesxe2x80x9d to Ramesh P. Rao, U.S. Pat. No. 3,756,839 xe2x80x9cMethod for Improving the Cellular Structure of Rigid Low Density Silicate Foamsxe2x80x9d to Ramesh P. Rao, U.S. Pat. No. 3,867,157 xe2x80x9cProcess for Manufacturing Granular Foamed Products of Silicaxe2x80x9d to Fukumoto et al. U.S. Pat. No. 3,870,496 xe2x80x9cMethod of Creating a Foamed Glass Product from Waste Glassxe2x80x9d to Ivan B. Cutler, U.S. Pat. No. 3,877,954 xe2x80x9cPorous Mouldingsxe2x80x9d to Bemd Wuistefeld, U.S. Pat. No. 3,951,632, xe2x80x9cMethod for Manufacture of Foam Glassxe2x80x9d to Seki et al., U.S. Pat. No. 4,080,187 xe2x80x9cFormation of Foamed Silicate Articlesxe2x80x9d to Donald R. Parnell, U.S. Pat. No. 4,124,365 xe2x80x9cMethod for Making Continuous Foam Glass Productxe2x80x9d to Williams et al., U.S. Pat. No. 4,347,326 xe2x80x9cFoamable Glass Composition and Glass Foamxe2x80x9d to Iwami et al., U.S. Pat. No. 4,395,456 xe2x80x9cInorganic Foamxe2x80x9d to Jackson et al., US. Patent xe2x80x9cMethod of Making Foam Glass from Diatomaceous Earth and Fly Ashxe2x80x9d to Hojaji et al., the entire contents of each of which are herein incorporated by this reference. Foamed glass formed by any of the known methods are then crushed to particles, again by any method known to those having skill in the art, including, but not limited to hammer milling, jet milling, and jaw crushing. The thus formed crushed foam glass may then utilized as a filtering aid for removing suspended materials in a fluid stream by first providing a permeable support with the crushed foam glass filter aid placed adjacent thereto, and directing the fluid stream having suspended materials through the filter. In this manner, suspended materials within the fluid stream are captured on the crushed foam glass filter aid, separating the suspended materials from the fluid stream. Additional benefits of the present invention may then be realized by removing the foam glass filter aid and the suspended materials as a mixture, melting the mixture to form a molten glass, fritting the molten glass to form a frit, comminuting the frit to form a foam glass precursor, mixing the foam glass precursor with a foaming agent, heating the foam glass precursor and the foaming agent to form a foam glass, and crushing the foam glass to reform the foam glass filter aid. This allows the suspended materials captured on the crushed foam glass filter aid to be removed from the foam glass filter aid, and the foam glass filter aid to be recycled and used again in the filtering process. Preferably, the step of melting the mixture to form a molten glass is performed in a high temperature waste treatment system capable of capturing inorganic portions of the suspended materials (such as metals) in a form which allows them to be separated and recycled, and capable of converting the organic portions of the suspended materials into gasses, which may then be further formed, for example through gas phase chemistry, into useful products such as synthesis gas. In this manner, the filtering aids and the suspended particles are converted to useful products, and/or recycled for further use.